WASHINGTON— Leaders of public health, environmental, academic, faith-based and other organizations today urged President Obama to do everything in his power to halt the largely unregulated expansion of hydraulic fracturing (“fracking”) to extract shale gas, a practice that has been linked to contaminated groundwater across the country.

“The lack of federal protections, combined with the current level and predicted increase of this activity, pose extreme and unnecessary risks to public health and the environment,” says the letter to the president. It also urges Obama to put the brakes on the practice “until and unless the environmental and health impacts of this process are well understood and the public is adequately protected.”

Fracking involves injecting a high-pressure mixture of water, sand and toxic chemicals under ground to break up rock formations to release methane gas.

The oil and gas industry has successfully lobbied to exempt fracking from several environmental laws, including the Safe Drinking Water Act and Clean Water Act. Companies that engage in fracking are not even required to disclose the nature and quantity of the more than 900 different chemicals used in the process.